The present invention relates to glass bending equipment. The bending equipment includes a plurality of rollers which are driven by a steel band which is positioned around drive and tension drums. The entire assembly is contained within an oven or lehr.
Conventional methods for bending glass plates includes sliding the glass plate over a plurality of roller surfaces and subjecting the glass to temperatures of 430xc2x0 C. The glass bending equipment is typically contained within a lehr or oven for sustaining the operating temperatures required to bend the glass plates. The glass bending equipment typically includes a set of drive and tension drums about which an Inconel steel band is placed. The steel band drives the plurality of rollers. The rollers are tilted at a desired angle to form a desired bending radius for the glass plates. The glass plates having an average temperature of 650xc2x0 C. bend under the weight of the glass and the thermal stresses of the high temperature environment to the desired radius.
It has been observed that a significant problem of band abrasion and subsequent failure occurs due to the combination of thermal stresses and twisting forces on the bands. One method employed for overcoming the above-referenced problem is to crown the surface of the drums. Crowning of the drum surfaces causes the band to seek the center of the drum and acts to prevent transverse motion of the band. Although this technique works in some band and drum applications, it is inadequate under the severe high temperature conditions of the glass making processes to prevent the band from moving transversely with respect to the drum and causing severe edge abrasion of the band when the band hits adjacent surfaces.
Therefore, there exists a need for a device which will prevent the band from abrading against surfaces adjacent to the band and drums. Further, the device should not interfere with the linear velocity of the band or impart excessive forces upon the band.
Accordingly, it is an object of the present invention to provide an improved band guide to prevent the edges of the band from abrading against adjacent surfaces.
Another object of this invention is to provide a band guide which does not significantly reduce the linear velocity of the band while preventing the band from moving transversely with respect to a drive and tension drums about which the band is positioned.
In accordance with these and other objects, the present invention provides a variable radius bending apparatus for bending a glass plate. The variable radius bending apparatus includes a bending rail having a longitudinal rail member and a drive drum and a tension drum rotatably attached thereto. A drive band is positioned around the drive drum and tension drum and in frictional engagement therewith.
A plurality of rollers are in driven contact with the drive band and are tiltable to a desired bend radius for forming the desired bend radius in the glass plate. Finally, a band guide is fixedly attached to the bending rail and in juxtaposition with the drive band for preventing the drive band from moving transversely with respect to the drive drum and tension drum, whereby the band is prevented from contacting a surface adjacent to the band.
The advantages accruing to the present invention are numerous. For example, the present invention prevents the edges of the drive band from abrading against surfaces adjacent to the drive band. The present invention increases drive band life and correspondingly increases manufacturing productivity of glass-making equipment by reducing machine down time caused by drive band failure. Furthermore, the present invention is configured to include easily replaceable components to reduce machine repair time.
The above objects and other objects, features, and advantages of the present invention are readily apparent from the following detailed description of the best mode for carrying out the invention when taken in connection with the accompanying drawings.